Glass fibers are typically protected from external forces with one or more coating layers. Typically, one or more coating layers (e.g., two or three coating layers) are applied during the optical-fiber drawing process (i.e., whereby a glass fiber is drawn from an optical preform in a drawing tower). A softer inner coating layer typically helps to protect the glass fiber from microbending. A harder outer coating layer typically is used to provide additional protection and to facilitate handling of the glass fiber. The coating layers may be cured, for example, using heat or ultraviolet (UV) light.
UV curing requires that the coated glass fiber be exposed to high intensity UV radiation. Curing time can be reduced by exposing the coating to higher intensity UV radiation. Reducing curing time is particularly desirable to permit an increase in fiber drawing line speeds and thus optical-fiber production rates.
As will be understood by those having ordinary skill in the art, curing occurs when UV radiation is absorbed by photoinitiators in the glass-fiber coating. After absorbing UV radiation, the photoinitiators decompose into free radicals, which promote the polymerization of the glass-fiber coating.
One of the problems of conventional UV-curing methods and devices, however, is that oxygen interferes with the polymerization of the glass-fiber coating by reacting with the free radicals. Therefore, a need exists for a UV-curing apparatus that is capable of curing glass-fiber coatings with improved curing efficiency.